Process for producing caprolactone



United States Patent ICC 3,546,251

Patented Dec. 8, 1970 3 546 251 taining an organic or inorganic acid and washing with water. 5E 2 3:Z EE E R EEE% ggg z$gg?gg After these treatments, e-caprolactone is catalytically Japan assignors to Chisso corporation, Osaka Japan: ring-opened by means of nascent hydrogen origlnated a corporation f Ja 5 from water, acid, alcohol or the like present in the sys- No Drawing. Filed May 24, 1967, Ser. No. 640,821 t rn, especially y the heatmg durmg the tune of vacuum Claims priority, application Japan, May 25, 1966, distillation, to form e-hydroxy caproic acid or to be con- 6 verted into oligomers and/ or polyesters of e-caprolactone (307d 9/ 00; Cosg 12/02 by condensation or polymerization. Accordingly, it is im- 260-343 9 Claims possible to obtain pure e-caprolactone in a better yield by means of distillation and purification of the system after a treatment such as the above-mentioned. ABSTRACT OF THE DISCLOSURE For the above-mentioned reasons, various studies have A method for producing E-caprolactone from the correbeen carfled out by the Present Inventors m order to sponding polymers of e-caprolactone by depolymerizing 15 cover 'Wlth a good efiiclency F'Faprolactone t. 011g them with heat in the presence of a suitable catalyst and omers and/or polyesters contammg not Fontammg at a temperature of 2l0-320 C. The starting materials, caprolactone and/or .G'hYdIPXY'CaPmIC acid and the polymers of epsilon caprolactone may contain method of the present mvent on has been completed. lactone and/or e hydroxy caproic acid Exemplary systems comprising oligomers and/orpolyesters of e-caprolactone containing or not containing 6- caprolactone and/or e-hydroxy-caproic acid in the present invention include the systems obtained after the re- This invention relates to a method for manufacturing moval of peroxides from the products in the above-mene-caprolactone by heating the corresponding polymers of tioned two methods for oxidizing cyclohexanone, the syse-caprolactone, containing or not containing e-caprolactern obtained after further treatment of said products, and tone itself and/or e-hydroxy-caproic acid, at 210-320 the system obtained by treating cyclohexanone hydro- C. in the presence of a catalyst. peroxide derived from the oxidation of cyclohexanone It has been known heretofore that e-caprolactone is with hydrogen peroxide as cyclohexanol hydroperoxide obtained by oxidizing cyclohexanone. Namely, various derived from the oxidation of cyclohexanol with active methods therefor have been known, one of them being oxygen, or the condensate between any one of the above a method of oxidizing cyclohexanone in the absence of mentioned hydroperoxides and cyclohexanone, with an water using a peracid such as peracetic acid, perbeuzoic acid such as concentrated sulfuric acid, acetic acid, hyacid or the like, and another being a method of oxidizing drofluoric acid or the like (rearrangement reaction cyclohexanone in an acidic or alkaline state using hydrooccurs). These systems are shown in the following forgen peroxide. mulas. Any systems other than the above-mentioned are Although e-caprolactone can be obtained in a better also included if they belong to the system containing yield by the former method, a considerable amount of oligomers and/or polyesters of e-caprolactone.

of E -caprolactone high boiling residual substances mainly composed of It has been heretofore known that a monomer can be oligomers and/or polyesters of e-caprolactone, is yielded, obtained by depolymerizing, on heating, a specified polyin case e-caprolactone is recovered by the distillation of ester in the presence of a catalyst. (W. H. Carothers the product. Therefore, an effective recovery of e-caproet al., J.A.C.S. 57, 929934, 1935.) However, it was also lactone from such high boiling substances has been shown in the report that the above-mentioned fact can desired. not always likewise be applied to various kinds of poly- On the other hand, in the latter method, only an exesters. tremely small amount of e-caprolactone is produced be- In fact, there was described that when polyesters of cause a large amount of e-hYdIOXY caproic acid and e-caprolactone was treated at 250 C. and 1-2 mm. Hg, oligomers and/or polyesters of e-caprolactone are formed. only a small amount of distillate (e-caprolactone) was Moreover, in this case, a considerable amount of cycloobtained (W. H. Carothers et a1., I.A.C.S. 56, 455, 1934). hexanone hydroperoxide or similar peroxide exists in the It has been found by the present inventors that oligoxidation products, and so the peroxides must be conomers and/or polyesters of e-caprolactone can be deverted to e-caprolactone and derivatives thereof, for expolymerized by heat at a temperature within specified ample, by warming these peroxides in an acidic state. range in the presence of a suitable catalyst to form e- Accordingly, the above-mentioned oxidation products caprolactone with an excellent yield. This recovery has must he usually treated, for example, by extracting them 7 0 been completed based upon the following experimental wtih a suitable solvent, subsequently allowing to stand, results:

Warming or heating them under an acidic condition con- (i) A mixture of 200 g. of e-caprolactone, 200 g. of

benzene and 300 cc. of 1 N sulfuric acid was refluxed on heating with stirring for 4 hours. Then, an organic layer was collected and washed with each 20 cc. of water six times, and thereafter benzene and water were removed therefrom under a reduced pressure to obtain 205 g. of a solid polyester (M.P. 3050 C.). To 100 g. of the poly ester thus obtained was added 1 g. of sodium hydroxide (1% to the polyester), and the mixture was heated with stirring. The greater part of the residual water (about 5 g.) was distilled off before the temperature reached 200 C. Additional heating to 260-320 C. yielded 86.5 g. of a fraction of (114-126 C./20 mm. Hg) (Yield: 91%). 84 g. of e-caprolactone (77-80 C./2 mm. Hg) was obtained by redistillation.

at 50 C. for 5 hours to carry out oxidation. Then, after unreacted cyclohexanone was removed from the reaction liquid by ether-extraction, the resultant residual liquid was treated with sodium hyposulfite, followed by warming in an acidic state, and adding potassium iodide, to decompose the formed peroxide perfectly. After the decomposition, the liquid was extracted with ether. The extract was dried over anhydrous sodium sulfate, followed by concentration. 132 g. of yellowish, viscous, oily substance was obtained.

100 g. of the oily substance was heated with stirring in 200 cc. of benzene in the presence of 1.5 g. of paratoluene sulfonic acid to azeotropically remove water. After washing of the residual oil with water and subsequent removal of the solvent under a reduced pressure,

The expeflment Was felxated, QPF that 0 there was obtained 95 g. of solid comprising oligomers sol'bitol ethylene glycol was p y as an lnltlatol' and polyesters of e-caprolactone. To 95 g. of the solid in i116 Polymerization of e'caprolactol'le, and the amount was added 1 g. of sodium hydroxide, and the mixture of Sodium hydroxide used in the P Y H Or! was heated with stirring. The greater part of the residual heating of the resultant polymer was altered. water had been distilled off before the bath temperature The results are shown in the following table: reached 260 C. Further by elevating the bath tempera- Initiator used Ethylene Sorhitol Sorbitol Sorbitol glycol Polyester:

ggiti i iiii iiii ifl 6.83 3.40 6.83 0.1

Amount of e-caprolactone 0 0.1116 g .25 72: 9 1 82: 5

Yield of e-caprolactone, percent From the table, it can be seen that oligomers and/or polyesters of e-caprolactone can be decomposed to some extent to form e-caprolactone, even in the absence of a catalyst, e.g., sodium hydroxide but the heating at a temperature within the range of the present invention in the presence of sodium hydroxide, markedly increases the yield of e-caprolactone.

An object of the present invention is to provide a method for recovering e-caprolactone with a good efficiency from the systems comprising the corresponding polymers of e-caprolactone by the depolymerization with heat.

Briefly speaking, the present invention consists in the method which comprises heating the corresponding polyesters of e-caprolactone, containing or not containing e-caprolactone and/or e-hydroxy-caproic acid, at 210- 320 C. in the presence of a suitable catalyst.

Amounts of the catalysts to be used are in the range of 0.55 parts, preferably 1-3 parts based on the weight of 100 parts of oligomers and/or polyesters of e-caprolactone. The decomposition is insuificient if the amount is smaller than 0.5 part, while the use of an amount larger than 5 parts is also not preferable because of the increased amount remaining as salt. The pressure to be employed may be atmospheric and subatmospheric pressure.

The heating temperature is in the range of 210- 320 C., and if a lower boiling substance such as water or others is contained in the reaction system, the treatment for removal of water or other lower boiling substances may be carried out beforehand at a temperature lower than the above-mentioned range, followed by decomposing with heat at a temperature within the range of the present invention. When the method of the present invention is carried out under preferable conditions, a-

caprolactone having a high purity can be obtained with a yield of as high as 80-95% by one treatment. If the conversion is insufiicient by one treatment, similar treatments may be repeated in order to increase the conversion.

EXAMPLE 1 Into 330 g. of 20% aqueous sodium hydroxide solution were simultaneously dropped 150 g. of cyclohexanone and 330 g. of aqueous hydrogen peroxide ture up to 260-320 C., g. of a fraction of 114 126 C./20 mm. Hg (yield: 89%) was obtained. 82 g. of e-caprolactone was obtained as a fraction of 7780 C./2 mm. Hg by redistillation.

EXAMPLE 2 One g. of sodium hydroxide was added to g. of the oily substance of Example 1 from which 'water had not yet been removed by azeotropic distillation, and then the mixture was heated with stirring to distill oflf residual water. Then, the distillation under 20 mm. Hg at a bath temperature of 260-320 C. yielded 85 g. of a fraction. 83 g. of e-caprolactone (8284 C./4 mm. Hg) was obtained (yield: 91%).

EXAMPLE 3 A high boiling residue was obtained when cyclohexanone was oxidized at about 40 C., with 15% solution of peracetic acid in ethyl acetate, using ethyl acetate as a solvent, followed by distilling. The resultant product was examined. To the high boiling substance mainly composed of polyesters of e-caprolactone, was added 1 g. of sodium hydroxide, and the mixture was heated to 300 C. as expressed by the bath temperature. e-caprolactone could be obtained with a yield of 92%.

EXAMPLE 4 A solution of peracetic acid in acetic acid was prepared at 40 C. in the presence of 4 g. of sulfuric acid from a mlxture of 360 g. of acetic acid and 100 g. of 30% hydrogen peroxide. After adding 5.6 g. of sodium phosphate, 80 g. of cyclohexanone was dropped into the resultant solution at 40 C. for 3 hours. The system after completion of the reaction was extracted with 200 cc. of ether, successively washed with water, water containing acid sodium sulfite and water, dried and evaporated to remove ether. 65 g. of a high boiling residue Was obtained. To 40 g. of the high boiling substance was added 0.35 g. of 1% sodium hydroxide. About 5 g. of dilute acetic acid was recovered by distillation. Heating to a bath temperature of 280 C. gave e-caprolactone with a yield of 93-94%.

Nextly, Example 2 was repeated, except that kinds of catalysts and amounts to be used were varied as follows:

In the case of non-catalyst, ring lactone (dimer) of caprolactone is obtained with a yield of about 35%.

In addition, the unconverted substances in the abovementioned examples could be converted into e-caprolactone by further repeating the same procedures.

What is claimed is:

1. A method for producing epsilon-caprolactone from the corresponding polymers of epsilon-caprolactone which comprises distilling by heating said polymers at a temperature from 210 to 320 C. in the presence of a catalyst selected from the group consisting of zinc acetate, cobalt acetate, and manganese acetate and recovering epsiloncaprolactone.

2. A method for producing epsiloncaprolactone from the corresponding polymers of epsilon-caprolactone which comprises distilling by heating said polymers at a temperature from 260 to 320 C. under a reduced pressure of about 20 mm. Hg in the presence of about 2 parts, based on the weight of 100 parts of the polymers of caprolactone, of a catalyst of zinc acetate and recovering epsilon-caprolactone.

3. A method according to claim 1 wherein said polymers further contain epsilon-caprolactone.

4. A method according to claim 1 wherein said polymers further contain epsilon-caprolactone and epsilonhydroxy-caproic acid.

5. A method according to claim 1 wherein said distilling by heating is carried out under a reduced pressure of about 20 mm. Hg.

6. A method according to claim 1 wherein 0.5-5 parts of catalyst based on 100 parts by weight of the polymer are present.

7. A method according to claim 1 wherein said catalyst is cobalt acetate.

8. A method for producing epsilon-caprolactone from the corresponding polymers of epsilon-caprolactone which comprises distilling by heating said polymers at a temperature from 210 to 320 C. in the presence of manganese acetate and recovering epsilon-caprolactone.

9. A method according to claim 8 wherein 0.5-5 parts of manganese acetate based on 100 parts by weight of the polymer are present.

References Cited UNITED STATES PATENTS 2,020,298 11/1935 Carothers et al 26098 FOREIGN PATENTS 1,411,213 8/1965 France 260-343 1,474,903 2/ 1967 France 260343 OTHER REFERENCES Hill et al.: JACS, 55:5031-9 (December 1933). Van Natta et al.: JACS 56:455-7 (February 1934).

HENRY R. JILES, Primary Examiner 5 C. M. SHURKO, Assistant Examiner US. Cl. X.R. 260--78.3 

